Packaging, especially flexible packaging, is useful to retain food and other consumer products for shipping and storage. Flexible film packaging can have many advantages. It can be manufactured at substantially lower cost than rigid containers, is light-weight resulting in reduced transportation costs, and can pack easily resulting in reduced storage space compared to other types of rigid packaging.
Despite these advantages, product freshness and containment within the package can be an issue when more product is provided than desired by a consumer for a single use. Several types of closures and fasteners are available for reclosing a previously opened flexible package. It is common to use mechanical reclosable fasteners, such as slide zippers, clips, tabs, interlocking strips, and the like. For example, some types of flexible packaging, such as vertically formed filled and sealed (VFFS) bagged product packaging, can provide various re-sealable zipper applications, such as plastic zippers sold under the trade name of ZIP-PAK (by Illinois Tool Works, Inc.). Nevertheless, use of this and other types of fasteners often requires complex manufacturing steps to apply, interconnect, and align the mechanical fastening feature of each structure. Further, packaging with zipper applications typically does not allow the package to reduce the headspace above the product as it is removed.
Adhesive-based reclosable fasteners, such as a pressure sensitive adhesive (PSA) can be an alternative to the mechanical fastener. In one attempt, a high-tack adhesive layer can be applied to a package web/film surface. The adhesive layer can be covered by a releasable liner that can be removed by a user when needed to close the package by rolling the film against the adhesive layer (See generally, U.S. Pat. No. 5,044,776 to Schramer et al.).
Adhesive-based fasteners can present challenges in both manufacturing and in consumer use. The adhesive can delaminate from the film substrate to which it is affixed rather than peel at its cohesive interface. Further, many PSAs have high tack levels. Tack is a property of an adhesive material that generally enables the material to form a bond with the surface of another material upon brief and/or light pressure. A high tack adhesive printed on the surface of a flexible film can cause problems during manufacturing in that the film used for packaging will not unwind freely from the roll stock. This is known as “blocking”. In use, particulate products contained within the flexible package (such as cookie crumbs, coffee, shredded cheese, and the like) can stick to the high tack PSA, thus reducing its adhesive effectiveness. Further, a consumer may find it undesirable to also stick to the PSA. One attempt to resolve this problem is the use of a lower tack PSA, though this has often increased the likelihood of delamination from the package film, as described above.